Preheat oven to 350 degrees. Grease an 8 or 9 inch cake pan, or spring form pan. Select a baking sheet or roasting pan in which the cake pan will set. (You will be adding water to the bottom of the sheet or roasting pan.) In a microwave safe bowl, combine chocolate chips with the butter. Melt at 45 second intervals, and stir until the chocolate and butter are fully melted and combined. With an electric mixer, beat the eggs for 6-8 minutes or until double in size. The eggs should be foamy and light colored. Pour the melted chocolate into a large bowl. Spoon one third of the whipped eggs into the chocolate and gently fold until combined. Add the remainder of the eggs into the chocolate and fold until completely combined. Pour mixture into prepared cake pan. If using spring form pan, seal the outside and bottom with aluminum foil and place in sheet or roasting pan. Place in oven. Pour 1-2 inches of hot water into the roasting pan. Bake for about 35 minutes or until a toothpick inserted in the middle comes up clean. Do not over bake. When done, let cool. (The cake will deflate.) Serve in wedges and garnish with powdered sugar, whipping cream or berries.